The in vitro enzymic hydroxylation of steroid hormones. 2. Enzymic 11β-hydroxylation of progesterone by ox-adrenocortical mitochondria

Abstract

Progesterone was found to be a more powerful inhibitor than 11-deoxycorticosterone (DOC) of certain reactions of the tricarboxylic acid cycle in ox-adrenocortical mitochondria. These inhibitions offer some explanation of the failure of steroid 11 [beta]-hydroxylation in the presence of progesterone, since this reaction in adrenocortical mitochondria appears to depend upon oxidative phos-phorylation for which members of the tricarboxylic acid cycle are oxidizable substrates. Conditions are described under which progesterone may be converted by ox-adrenocortical mitochondria into 11 [beta]-hydroxyprogesterone as the main product, and to traces of a more polar product which reduces tetrazolium blue. The choice of suitable enzyme preparations and the influence of steroids on enzymes are discussed in relation to the physiological significance of steroid reactions observed in vitro.